An example of a conventional wafer transfer device is disclosed in Japanese utility model laid open publication (kokai) No. 2-41436. According to this conventional device, a carriage carrying a plurality of wafer support plates is moved longitudinally by a low speed electric motor, and a table supporting a wafer basket is moved vertically by another low speed motor. Thus, by appropriately synchronizing the horizontal movement of the carriage with the vertical movement of the basket support table, it is possible to transfer a plurality of wafers from one basket to another.
Such a device is required to be free from contaminants because semiconductor wafers become easily unusable when contaminated by extremely small amounts of chemicals and particles. The use of electric motors requires an associated control circuit and, possibly, a microprocessor for controlling the operation of the electric motors. Thus, a significant cost will be necessary to construct such a device.